The third generation partnership project (3GPP) Release 6, introduced high-speed uplink packet access (HSUPA) to provide higher data rates for uplink transmissions. As part of HSUPA, a new transport channel, the enhanced dedicated channel (E-DCH), was introduced to carry uplink (UL) data at higher rates. Along with the E-DCH, new MAC sub-layers were introduced within the overall wireless transmit/receive unit (WTRU) to control the E-DCH transport channel. The new MAC sub-layer is the MAC-e/es. More specifically, the MAC-e/es is the MAC entity that handles the data transmitted on the E-DCH. Upper layers configure how the MAC-e/es is to be applied to handle E-DCH functionality.
A block diagram of the UMTS Terrestrial Radio Access Network (UTRAN) MAC-e layer architecture is shown in FIG. 1, a block diagram of the UMTS Terrestrial Radio Access Network (UTRAN) MAC-es layer architecture is shown in FIG. 2, and a block diagram of the WTRU MAC-e/es layer architecture is shown in FIG. 3.
For each WTRU that uses the E-DCH, one MAC-e entity per NodeB and one MAC-es entity in a serving radio network controller (SRNC) are configured.
FIG. 1 shows a UTRAN MAC-e 100 and a E-DCH scheduling entity 110. The MAC-e 100 is located in a NodeB and controls access to the E-DCH. There is one MAC-e 100 in the NodeB for each WTRU. There is only one E-DCH scheduling entity 110 in the NodeB. The E-DCH scheduling entity 110 manages E-DCH cell resources between WTRUs.
The UTRAN MAC-e 100 shown in FIG. 1 comprises an E-DCH control entity 120, a de-multiplexing entity 130, and a hybrid automatic retransmission request entity (HARQ) entity 140. The MAC-e 100 and the E-DCH scheduling entity 110 handle HSUPA specific functions in the NodeB.
The UTRAN MAC-es 200 shown in FIG. 2 comprises a reordering queue distribution entity 210, a reordering/combining entity 220, and a disassembly entity 230. The UTRAN MAC-es 200 further comprises a macro diversity selection entity in FDD mode when there is soft handover with multiple NodeBs. The MAC-es 200 is located in the SRNC and handles E-DCH specification functionality that is not covered in the MAC-e in the NodeB. The MAC-es 200 is connected to both the MAC-e and the MAC-d.
FIG. 3 shows a block diagram of the WTRU MAC-e/es layer architecture. The WTRU MAC-e/es 300 comprises a HARQ entity 310, a multiplexing and transmission sequence number (TSN) setting entity 320, and an enhanced transport format combination (E-TFC) selection entity 330.
The HARQ entity 310 handles the MAC functions relating to the HARQ protocol. Specifically, the HARQ entity 310 is responsible for storing MAC-e payloads and re-transmitting them. The detailed configuration of the HARQ protocol is provided by the radio resource control (RRC) over the MAC-control service access point (SAP).
The multiplexing and TSN setting entity 320 concatenates multiple MAC-d protocol data units (PDUs) into MAC-es PDUs. Further, the multiplexing and TSN setting entity 320 multiplexes one or more MAC-es PDUs into a single MAC-e PDU, to be transmitted in a next transmission time interval (TTI), as instructed by the E-TFC selection entity 330. The multiplexing and TSN setting entity 320 is also responsible for managing and setting the TSN per logical channel for each MAC-es PDU.
The E-TFC selection entity 330 is responsible for E-TFC selection according to scheduling information, relative grants and absolute grants, received from the UTRAN via L1 signaling and a serving grant value signaled through RRC. The E-TFC selection entity 330 is also responsible for arbitration among the different flows mapped on the E-DCH. The detailed configuration of the E-TFC selection entity 330 is provided by RRC over the MAC-control SAP. As stated above, the E-TFC selection entity 330 controls the multiplexing function of the multiplexing and TSN setting entity 320.
Currently, the MAC-e/es selects a number of MAC service data units (SDUs) from each logical channel and multiplexes the MAC SDUs into a single MAC-e PDU for transmission. The existing MAC-e/es protocol relies on the fact that the RLC is configured to deliver PDUs in one or more predefined sizes. Unfortunately, the use of predefined PDU sizes creates overhead at higher data rates.
Accordingly, there exists a need for improved MAC-e/es architecture in both the UTRAN and WTRU that allows for flexible PDU sizes at the radio link control (RLC) layer and PDU segmentation at the MAC layer. The use of flexible PDU sizes and PDU segmentation would allow for higher data rates in the UL and may reduce header overhead for UL transmissions.